In recent years, communication technology has widely spread in terms of the number of users and amount of use of the telecommunication services by the users. This also led to an increase in the number of different technologies and technological concepts in use. In particular, two main areas of communication experienced overly large increases in the past years.
One of these areas is mobile communications and mobile communication networks. In this connection, the evolution from Second Generation (2G) mobile communication systems towards Third Generation (3G) mobile communication systems is particularly worth mentioning. Among others, this includes the development of systems such as the General Packet Radio Service (GPRS), the Universal Mobile Telecommunications System (UMTS) and cdma2000 as an example of a system being based on a code division multiple access (CDMA) radio technology. The term cdma2000 is to be understood to represent a family of standards describing the use of CDMA in a way to meet the requirements of 3G communication systems as defined in IMT-2000, for example.
The other area comprises Internet communications, which includes communications being based on the Internet Protocol (IP) as a communication protocol used and/or being accomplished in networks being based on the Internet Protocol. Thereby, the Internet Protocol being specified by the Internet Engineering Task Force (IETF) proved to be seminal, especially in wired and fixed-line communications. In this regard, IP is mentioned only as an example of packet-based communication protocols, and of course others are also conceivable.
Further, there can be observed a trend in merging of different technologies and technological concepts, which have been previously used separately. For example, IP is one of the proposed and favored communication protocols for future mobile communication systems.
Thus, two of the main areas of communication, i.e. mobile communications and Internet communications, are about to grow together. Therewith, new chances and prospects arise for future services. However, since the single technologies in both areas are not designed to comply with each other for a seamless cooperation, a multitude of problems and requirements will also arise.
The Internet Protocol deployed globally today is primarily Internet Protocol version 4 (IPv4). In IPv4, the address space of available network addresses for the participating communication entities is relatively limited. In more detail, since the IP address field of IP version 4 has a length of 32 bits, there exist 232 available IP addresses. With the above-mentioned rapid growth and expansion of the Internet and the number of hosts connected to the Internet, the addresses available in IPv4 have been depleted significantly, i.e. by more than 50%.
Additionally, an increasing interconnection of previously not interconnected devices of all kinds can be expected for the near future. For example, sensor networks consisting of hundreds of sensor devices are expected to be built up. In this connection, one vision resides in that all electronic devices will sometime be interconnected with each other worldwide. For the communication between these devices, IP is the favorite choice of communication protocol. With such prospects, the shortage of IP addresses will become even more urgent within the next few years.
In order to overcome the problem of the current address space running out, a new version of the Internet Protocol called Internet Protocol version 6 (IPv6) has been standardized in the IETF. In IPv6, the address space of available network addresses for the participating communication entities is much larger. In more detail, since the IP address field of IP version 6 has a length of 128 bits, there exist 2128 available IP addresses. Furthermore, IPv6 has advantages in e.g. auto-configuration, mobile IP applications and automatic renumbering.
The limited availability of IPv4 addresses and the increasing growth of IP capable mobile devices makes the problem of assigning globally routable IPv4 addresses challenging if not impossible. The only solution today is to assign private IP addresses which are defined in RFC1918. Hence, Network Address Translators (NATs) would have to be used for mapping private and public IP addresses with each other in order to overcome the shortage problems. However, this brings in a multitude of problems. While it is possible to overcome the issues that NATs present, it does require additional equipment, modifications to applications, gateways etc. To the contrary, as mentioned above, IPv6 does not have the address shortage problem that IPv4 presents and hence is the more favorable approach as a long-term solution.
An end-to-end IPv6 connectivity enables a deployment of services based on the Session Initiation Protocol (SIP) as well as peer-to-peer applications in a much easier manner since issues associated with Network Address Translators (NATs) would not have to be dealt with. This is why the present application emphasizes the focus on the usage of IPv6. However, other protocols may still comply with the idea as conceived with the present invention. That is, the present invention is not limited to be applied to IPv6.
For transition from the current IPv4-based networks and hosts to such based on IPv6 there are a number of mechanisms and means to be introduced, some of which have already been developed. Further, it is unavoidable that both protocols are being used in parallel for some time. In the following, an example scenario for problems occurring by a simultaneous usage of Internet Protocol applications of different versions will be outlined.
In the Third Generation Partnership Projects 3GPP and 3GPP2, there is specified a so-called IP Multimedia Subsystem (IMS). The IMS essentially creates a SIP infrastructure for packet networks such as GPRS/UMTS and cdma2000. The IMS enables the creation and deployment of various types of applications and services that use SIP. These applications can be realtime, non-realtime, multimedia and others. The IMS is the service core of the 3G packet networks. Therewith, operators of Public Land Mobile Networks (PLMNs) such as UMTS or cdma2000 can offer their subscribers services based on and built upon packet data networks that are primarily based on IP. IMS deployments are expected to occur in the near future. This implies that terminals will need to connect and communicate with the IMS network elements via IPv6 protocols.
However, mobile communication systems such as cdma2000 networks that are currently deployed in many countries primarily (or even exclusively) support IPv4 as well as IPv6 as the communication protocol. Terminals such as mobile stations will be dual-stack (DS) capable, i.e. they will have both an IPv4 protocol stack and an IPv6 protocol stack built in for being able to communicate via IPv4 and IPv6. As a result it is possible that the access network to which the terminal connects can be based on IPv4 only. However, it is still possible to establish an IPv6 session with an IPv6-based IMS. This would be enabled by encapsulating (tunneling) IPv6 packets as IPv4 payload in IPv4 packets, transmitting these IPv4 packets through the access network, and subsequently decapsulating the IPv6 packets out of the IPv4 packets at a DS router in the network.
In order to enable this, a dual-stack router is needed, which supports both IPv4 and IPv6 and is capable of encapsulation and decapsulation of IPv6 packets. Such a dual-stack router can be arranged somewhere in the core network and may not necessarily be “visible” to the access network and, thus, to a terminal being connected to the access network. In many instances the dual-stack router may be in the home network of the operator and the visited or foreign network even may not have any such router.
The terminal needs to be aware of a dual-stack (DS) router in the network, which dual-stack router is capable of encapsulation and decapsulation of IPv6 packets transmitted to and from the terminal. Thus, the host or terminal needs to discover the network address of this dual stack router in order to use IPv6 via encapsulation over an IPv4 network such as a conventional radio access network.
In prior art, the discovery of a dual-stack router has already been addressed previously, e.g. by the IETF.
Current solutions involve the use of multicast or configuring of the dual-stack (DS) router with an anycast address. Solutions based on Domain Name System (DNS) and Dynamic Host Configuration Protocol (DHCP) are also found to be possible.
However, a mobile communication network, e.g. the cdma2000 packet data network, presents a different architecture as compared to standard IP networks. Since the hosts are connected over an air interface that is operated in the licensed bandwidth spectrum, it is critical that discovery and configuration of such servers is done as optimally as possible e.g. as regards bandwidth efficiency. Yet, the proposed solutions can not fulfill these requirements and, therefore, are unfavorable in this connection.
It is also possible that a preconfigured address of the dual-stack router can be used. However this does not provide an optimal solution since the operator would have to deploy a certain number of dual-stack routers based on the number of subscribers rather than the number of active users at any given time. Also a load-balancing and an optimal location of the router cannot be achieved this way.
Solutions to the problem of discovering a dual-stack router, e.g. a DS IPv4/v6 transition router, have also been presented in the IETF, However, without a focus on the special requirements and needs of mobile communication systems.